Conventionally, as one of the crystal growing methods, a hydride vapor phase epitaxy (HVPE) is known, in which by using a metallic chloride which is generated by a reaction of a heated metallic source material with a hydrogen chloride as source material gas, a crystal is grown from the chloride gas and hydroxide gas of a nonmetallic material.
FIG. 3 is a schematic configuration diagram showing the structure of a conventional vapor phase growing apparatus (an HVPE apparatus).
An HVPE apparatus 100 is configured with a reacting furnace 1 which is sealed, and resistance heaters 2 which are provided at an outer circumference of the reacting furnace 1. The reacting furnace 1 is provided with an HCl gas supplying pipe 6 to supply HCl gas to generate a group III source material gas; a group V source material gas supplying pipe 7 to supply group V source material gas such as NH3 gas, and the like, into the reacting furnace; an N2 gas supplying pipe 8 to supply N2 gas into the reacting furnace; a gas discharging pipe 3; and a substrate holder 4 to place a substrate 11.
Further, a source material placing section 10 is provided in the HCl gas supplying pipe 6, and a metallic source material 9 is disposed at this section to generate the group III source material gas. Moreover, the group III source material gas which is generated by the reaction of the HCl gas with the metallic source material 9 is sprayed onto the substrate 11 through a supplying nozzle 12.
In a metal-organic vapor phase epitaxy (MOVPE), a cold-wall heating method is applied, in which only the circumference of the substrate is directly heated, and the wall temperature of the reacting furnace does not rise. On the other hand, as shown in FIG. 3, a hot-wall heating method is applied in the HVPE apparatus 100, in which the entire reacting furnace is heated. That is to say, the HVPE method is designed to heat an area from a source material section in which the metallic source material is provided, through a mixing section in which the source material gas is mixed, to a growing section in which the reaction is proceeded so as to grow the crystal. The HVPE method has an advantage in that the crystal can be grown in a relatively high speed by supplying the source material gas on a massive scale.
Generally, in a case where a crystal of a gallium nitride (GaN) is grown by applying the HVPE method, a gallium chloride (GaCl) which is generated by the reaction of a metallic gallium (Ga) with a hydrogen chloride (HCl) is used as the group III source material, and an ammonia (NH3) is used as the group V source material. Here, the thermal decomposition rate of the ammonia is said to be a few %, which is lower compared to that of an arsine (AsH3) which is used as the group V source material when a crystal of a gallium arsenide (GaAs) is grown, and to that of a phosphine (PH3) which is used as the group V source material when a crystal of an indium phosphide (InP) is grown. Accordingly, it is inevitably necessary to enlarge the proportion of V/III which is the supplying proportion of group V source material to the group III source material, when the crystal of GaN single crystal is grown.
Consequently, when the crystal of GaN single crystal is grown by applying the HVPE method, the following reaction pipe configuration is employed, as shown in FIG. 3. That is, a massive NH3 is gradually supplied from the group V source material gas supplying pipe 7, so as to be a laminar flow in the entire reacting furnace, and a small amount of GaCl which is generated by the reaction of the HCl with metallic Ga 9, is sprayed onto the substrate 11 in the growing section by the nozzle 12.
Further, Patent Documents 1-5 disclose that a rare earth group 3B perovskite substrate, especially an NGO substrate, is useful for the substrate for growing a GaN system compound semiconductor single crystal.    Patent Document 1: Japanese Patent Application Laid Open Publication No. 8-186329    Patent Document 2: Japanese Patent Application Laid Open Publication No. 8-186078 (Japanese Patent No. 3263891B)    Patent Document 3: Japanese Patent Application Laid Open Publication No. 8-208385 (Japanese Patent No. 3564645B)    Patent Document 4: Japanese Patent No. 3293035B    Patent Document 5: Japanese Patent Application Laid Open Publication No. 9-071496 (Japanese Patent No. 3692452B)    Non-Patent Document 1: Journal of Crystal Growth 246 (2002) 215-222